Micro-discharge truing device and fine machining method using the device

Abstract

There are provided an electrically conductive grindstone 12 for machining a workpiece 1, a disc-shaped discharge electrode 14 having an outer peripheral edge 14a which can be disposed in the vicinity of a machining surface 12a of the grindstone, an electrode rotating unit 16 for rotating the electrode around an axial center Z, a position controller 18 for controlling a relative position of the outer peripheral edge of the electrode and the grindstone, a voltage applying unit 20 for applying a predetermined voltage between the grindstone and the electrode in a pulse manner, and a machining liquid supply unit 22 for supplying an alkaline liquid between the grindstone and the electrode. By stably generating micro-discharge between the outer peripheral edge 14a of the rotating discharge electrode 14 and the machining surface 12a of the electrically conductive grindstone 12, a metal bonded portion of the electrically conductive grindstone is molten/removed with no contact therewith and with high efficiency and precision, and a grindstone surface is corrected to a desired shape.

What is claimed is:  
     
       1. A micro-discharge truing device, comprising: 
       an electrically conductive grindstone for machining a workpiece;  
       a disc-shaped discharge electrode having an outer peripheral edge disposable in the vicinity of a machining surface of the electrically conductive grindstone;  
       an electrode rotating unit for rotating the discharge electrode around an axial center Z;  
       a position controller for controlling a relative position of the outer peripheral edge of the electrode and the grindstone;  
       a voltage applying unit for applying a predetermined voltage pulse between the grindstone and the electrode; and  
       a machining liquid supply unit for supplying an alkaline liquid between the grindstone and the electrode.  
     
     
       2. The micro-discharge truing device according to claim  1 , wherein said voltage applying unit comprises: 
       a direct-current power supply for generating a predetermined direct-current voltage;  
       a pulse discharge circuit having a capacitor C, a resistance R, and a pair of output terminals to charge the capacitor when the terminals are open therebetween and to discharge electricity from the capacitor when a resistance between the terminals is reduced; and  
       a current supply line for connecting a plus side of said output terminal to the grindstone and connecting a minus side to the electrode.  
     
     
       3. A fine machining method, comprising the steps of: 
       (A) micro-discharge truing with a disc-shaped discharge electrode having an outer peripheral edge which can be disposed in the vicinity of a machining surface of an electrically conductive grindstone, and an electrode rotating unit for rotating the discharge electrode around an axial center Z, for supplying an alkaline liquid between the grindstone and the electrode, and simultaneously applying a direct-current voltage pulse between the electrically conductive grindstone and the discharge electrode in a pulse manner to shape the machining surface by discharge;  
       (B) electrolytic dressing with a dressing electrode having opposite surfaces distant from the machining surfaces of said electrically conductive grindstone for supplying the alkaline liquid between the grindstone and the dressing electrode and simultaneously applying the direct-current voltage between the electrically conductive grindstone and the dressing electrode to dress the electrically conductive grindstone by electrolyte; and  
       (C) machining a workpiece with the electrically conductive grindstone.